The invention concerns novel separators for storage batteries and the use of separators in gel storage batteries.
Storage batteries with alternately positive and negative electrode plates use separators for the separation of the electrode plates, the separators preventing direct contact between the plates and thus a short-circuit.
Essentially a distinction is to be drawn between two kinds of storage batteries: gel storage batteries (sealed storage batteries) which contain the electrolyte, usually sulphuric acid, in a condition of being bound into a gel, usually a thixotropic silica gel, and liquid storage batteries (closed storage batteries) in which the electrolyte is present in the form of a liquid.
In closed storage batteries, besides simple separators in layer form, separation of the electrode plates is also effected by using pocket separators in which the electrode plates are disposed in a pocket or casing of separator material. Particularly in relation to the positively charged electrode plates that has the advantage that the electrode slurry which is produced there is caught and does not come into contact with the adjacent negative electrode plates. In addition pocket separators also afford better protection from short-circuits as they surround the electrode plates at the edges and peripheral surfaces. Slipping of the separator therefore does not result in regions of the electrode plates being exposed, with the danger of a short-circuit.
Gel electrolyte storage batteries (sealed storage batteries), for example with positive grid plates, generally use leaf separators comprising phenolic resins, PVC, PE, latex or coarse glass fibres. For optimum filling of the storage battery with gel those leaf separators can have special have special surface structures and, on the side facing towards the positive electrode plate, frequently have a glass fibre mat which is laminated thereonto and which provides a reinforcing effect, by which the positive material which slurries out is mechanically stabilised and thus longevity in the case of frequent charging and discharging cycles is improved.
The disadvantage of those leaf separators is that they are highly expensive by virtue of the materials used and large amounts of material have to be used to achieve adequate stiffness. The leaf separators are difficult to handle and as a result incur a high level of complication and expenditure upon packaging and upon removal from the packaging and high levels of consumption of packaging material. In addition, with that kind of separators, there is a need for additionally protecting the electrode plates at the peripheral surfaces and edges and they have a comparatively high resistance.
Pocket separators have hitherto been used only in relation to liquid storage batteries (closed storage batteries). Use of the pocket separators, known for that purpose, for gel storage batteries (sealed storage batteries) was hitherto not possible as, when using those known pocket separators, homogenous distribution of the gel electrolyte is prevented by the pockets and as a result the service life and quality of the storage battery would have been considerably impaired.
Therefore the invention is based on the problem of providing less expensive separators for the separation of plate electrodes in gel storage batteries, which have a low electrical resistance and which afford additional protection for the edges and side surfaces and at the same time permit homogenous gel filling of the storage battery.